You can easily get very decent rooms for that price.
I will give you the details soon on Hotels we booked but advice you to keep checking on booking.com and even others.
However for Thekkady, I think we booked a perfect hotel. Very close to the national park and good rooms.
Kerala is still pretty cheap from Tourist point of view also from what I found out and was actually surprised.
And him going in off season ( Munnar may be crowded as it is like hill station for Kerala people from the hot weather) but rest places will be much cheaper.